Q. Can Catholics receive communion in a non-Catholic ceremony?
R. Catholics believe that the Eucharist is a sign of unity. This is one of the reasons that Protestants can’t ordinarily receive Communion in Catholic churches. The same holds true in the opposite direction: For a Catholic to receive Protestant communion would not only give the impression that the Protestant version is valid, but it would also create a false sense of unity. There is no true unity between us sadly and for us to receive communion in a Protestant church would be lying with our bodies. Almost as if we would say yes by bobbing our heads up and down in the affirmative but saying no with our words. We would be giving a mixed message, and a confusing one. And therefore lend confusion as to what the Catholic Church actually teaches on the matter.
And that, my friend, is the main reason a Catholic Christian shouldn’t receive communion in a non-Catholic church. The Catholic Church teaches in the True Presence of our Lord in the Eucharist, most other churches do not believe in this change. For a Catholic to receive communion in a non-Catholic church would be saying to the other Christians of that church that he believes as they do. The Eucharist is the source and summit of our faith. Everything revolves around this fact, the fact that Jesus Christ is actually present in the consecrated bread and wine. We would be doing a great disservice to those Christians by going along with their ideology. We ought to provoke their thinking instead and to wake them up from their complacency by simply not partaking of communion and keeping to the truth. In fact, we are not in full communion with each other yet and pretending that we are is not helpful for any member of His Church.